Temperature Difference Effect on Heat Point Circuit in the Heating Network

Reducing the calculated water temperature in the heating network can lead to a significant increase in its consumption. One of the most effective measures to reduce the water flow rate in the heating network is to increase the calculated difference in water temperatures in the heating system. This is possible if the calculated water temperature in the return line is reduced. The literature mainly considers only the economic component of this solution.

Purpose: Studying the possible reduction in the water flow rate by increasing the temperature difference in the heating network while ensuring the required temperature of internal air in the premises.

Methodology: In heating point circuits, it is recommended to use two-stage circuits in which the return line heat is used to preheat tap water for the hot water supply. In low-temperature heating systems, the return line heat can be insufficient, so a single-stage parallel hot water supply heat exchanger can be more efficient. Calculations are performed for the heating station with the different ratio between the maximum thermal power of hot water supply and heating, different design temperatures of supply and return water for two- and single-stage heat point circuits.

Research findings: In the case when the estimated heat load of hot water supply is 40 to 60 %, the best temperature regime in the premises is provided by a single-stage parallel circuit of hot water supply heat exchangers at 40 °C temperature of return line water in the heating system. If the heating load of the hot water supply ranges from 60 to 80 %, it is advisable to use the two-stage mixed circuit at 40 °C water temperature in the return line. If the heating load is higher than 80 %, it is possible to use the two-stage mixed circuit at 70 °C water temperature in the return line.

Value: The selected heat point circuit is the best for both economy and thermal engineering, depending on the ratio between the thermal power of hot water supply and heating and calculated temperatures of water in the heating network.

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